it only happens on the last figure of a three figure number - this reverts to a lining style figure from the non-lining style intended
I have tried setting up both Paragraph and Character styles to use Open Type 'Proportional Oldstyle' feature
The font I have been using is Sabon LT Std - and -
LO & BEHOLD!
On Adobe Community I have found that the LT Std font has been superseded by a Sabon Pro - and I suspect that's the issue, as when I changed the font on the folios the problem disappeared
You should always use Paragraph Styles. Character Styles are only for local differences to the underlaying paragraph style.
The page number paragraph style must be defined and used. Often it is the alignment relative to the spine is useful, so you can use the same style on the left and right pages, used on master/parent pages on the most top layer.
Another question: did you check, if the font is installed on several places in different versions. It could happen that InDesign pick different fonts from different generations so that the OTF functionality is not picked up for every digit?
Thanks. Font is designed by me. inDesign is the very last version. I think font is not the problem. If I digit the same number in a new text box in the same doc and assigne the opentype features there is no issue (see attach). If I made a new book file on my desktop everything works fine (see attach). Could be possible the issue is because I'm working directly on creative cloud server?
What do you mean by "I'm working directly on creative cloud server"? Does that mean you're storing your files in the folder which appear on your drive as "Creative Cloud Files" (see image)?